The present invention relates to sound generators, particularly, but not exclusively, to sound generators for fire alarm systems, security systems and the like.
According to one aspect of the present invention there is provided a sound generator comprising a three dimensional body defining a cavity closed at one end and open at the other, a crystal attached to the surface of the closed end and oscillator means operative to pulse the crystal to cause the body to vibrate.
According to another aspect of the present invention there is provided a sound generator comprising a diaphragm, a crystal attached to one face of the diaphragm and oscillator means operative to pulse the crystal to cause the diaphragm to vibrate, the oscillator means comprising at least one CMOS circuit.
In order that the invention may be more clearly understood, one embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings.